As someone who is attracted to a very wide variety of physiques and features, I've been contemplating different measurements to better understand what level of size difference is feasible. So how can a large penis fit in a tiny body naturally? If we go deeper than the fictional imagery explanation, we must take anatomy into account. The internal structure of a "character" could be very different from traditional humans, allowing for the possibility of significantly more vaginal depth and stretchiness.
One example of anatomy different from traditional humans is the facial structure of most anime characters - the shape and size of their eyes, nose, and mouth. Many people have the idea that a character appearing "realistic" means that alongside the "graphical enhancements", their facial features are warped to match the structure of traditional humans. My personal definition of a realistic loli is a character appearing hyper-realistic while completely retaining the anime-style structure of their face.
This is how lolis appear in my dreams. The best way I can describe them is that they look hyper-realistic, like real people, but at the same time their facial structure and hairflow matches their original anime appearance; they also have individual teeth and strands of hair. I have yet to see an accurate depiction of a "realistic loli" on the internet - I have attempted to create some with my Loli Party portraits, but didn't even come close. Regardless, they express the concept sufficiently. Perhaps in the future, there will be technology that allows me to export images and video from my dreams so I can share examples of what I call "realistic lolis".
Any time I see lolis in my dreams, I am filled with indescribable levels of love and excitement. Speaking of dreams, in one dream, I naturally went balls-deep inside a loli, the tip of my penis reaching her chest. I would love to explore this with even smaller girls, seeing what level of size-difference penetration is experientially feasible for different anatomy types, (stretching out from the stomach, or from the chest).
Now, beyond dreams, how far can size difference realistically be taken in this physical reality? Theoretically speaking, let's say 90cm tall loli extraterrestrials visited Earth. It is very possible that their anatomy differs enough for their vaginal depth to reach their neck. How about lolis 20cm tall? The stretchiness is not too farfetched - on this planet, the octopus provides an example of super stretchy skin, being able to stretch up to six times its normal size. But even with that level of stretchiness, is it possible to have vaginal sex with physical humanoids that small? Could their body function properly while also having the space to take a penis larger than their torso? Perhaps it's possible, perhaps not - I am no ET biologist, I am just sharing ideas that interest me.
I believe it's highly probable that 90cm lolis could take it balls-deep, but I have no expectations when it comes to physical lolis 20cm tall. However, if there are lolis that size who are partially physical/nonphysical, I believe that there is a possibility that they could fit a penis larger than their torso.
Even if that doesn't end up being the case, it is still possible to play with these ideas in the dream dimension, where there are no limitations other than the ones you impose on yourself. At this time, I struggle with dream vividness, lucidity, and stability, so I have not yet experienced sex with a super tiny girl, but I plan to in the future.